BEPUphysics VS awesome-monogame

The best pure-C# physics library (hands-down) is bepuphysics2, which unfortunately is mainly a 3D physics library, but could be used for 2D if you wanted to get your hands dirty.

Bepu Physics is pretty good and is written in really optimized C#, the author's blog post are really interesting to read.

The usual approach is some form of sweep to get a time of impact. Once you've got a time of impact, you can either generate contacts, or avoid integrating the involved bodies beyond the time of impact, or do something fancier like adaptively stepping the simulation to ensure no lost time.

If the details don't matter much, it's common to use a simple ray cast from the center at t0 to the center at t1. Works reasonably well for fast moving objects that are at least kinda-sorta rotationally invariant. For two dynamic bodies flying at each other, you can test this "movement ray" of body A against the geometry of body B, and the movement ray of body B against the geometry of body A.

One step up would be to use sphere sweeps. Sphere sweeps tend to be pretty fast; they're often only slightly more complicated than a ray test. Pick a sphere radius such that it mostly fills up the shape and then do the same thing as in the previous ray case.

If you need more detail, you can use a linear sweep. A linear sweep ignores angular velocity but uses the full shape for testing. Notably, you can use a variant of GJK (or MPR, for that matter) for this: http://dtecta.com/papers/jgt04raycast.pdf

If you want to include angular motion, things get trickier. One pretty brute forceish approach is to use conservative advancement based on distance queries. Based on the velocity and shape properties, you can estimate the maximum approaching velocity between two bodies, query the distance between the bodies (using algorithms like GJK or whatever else), and then step forward in time by distance / maximumApproachingVelocity. With appropriately conservative velocity estimates, this guarantees the body will never miss a collision, but it can also cause very high iteration counts in corner cases.

You can move a lot faster if you allow the search to look forward a bit beyond potential impact times, turning it into more of a root finding operation. Something like this: https://box2d.org/files/ErinCatto_ContinuousCollision_GDC201...

I use a combination of speculative contacts and then linear+angular sweeps where needed to avoid ghost collisions. Speculative contacts can handle many forms of high velocity use cases without sweeps- contact generation just has to be able to output reasonable negative depth (separated) contacts. The solver handles the rest. The sweeps use a sorta-kinda rootfinder like the Erin Catto presentation above, backed up by vectorized sampling of distance. A bit more here, though it's mainly written for users of the library: https://github.com/bepu/bepuphysics2/blob/master/Documentati...

I use https://github.com/bepu/bepuphysics2. I haven't worked with 3d physics engines before so I can't really comment on it's quality but it is definitely an impressive project! The developer is very active and helpful and some of the demo scenes are pretty large and complex.

XNA re-implementation/extended support seems like a good idea. I'll look into it some more. I also want to share this list of libraries suggested to me for MonoGame support: https://github.com/aloisdeniel/awesome-monogame

I don't have anything to add to Ignatus other than a GitHub repo filled with resources that can help you out.

awesome-monogame

Awesome Monogame has a nice list of tutorials

If you want to avoid duplicating work in the future (and also find some awesome libs), checkout Awesome Monogame: https://github.com/aloisdeniel/awesome-monogame.

awesome-monogame/README.md at master · aloisdeniel/awesome-monogame

Fair warning, base Monogame leaves a lot to you to create yourself. It's technically a framework and not an engine (difference explained here). However, there are several extensions that add specific things you might want.

And as for replacing libraries, I obviously don't know what you've got going on, but there are a bunch of extensions to Monogame that add all sorts of stuff. Maybe there's something in the you can use to help you?